I am bit confused about HDFS storage and Data node storage. Below are my doubts.
1. Map function output will be saved to data node local disk and reducer output will be sent to HDFS. As we all know that data blocks are stored in data nodes local disk is there any
other disk space available for HDFS in data node??
2. What is the physical storage location of reducer output file (part-nnnnn-r-00001) ? will it be stored in Name node hard disk?
So my assumption is data node is part is of HDFS i assume data node local disk is also part of HDFS.
I would make a summary that I think it may help you. the Map input OR Reduce output can be from any source (local hist or HDFS, for this example). You configure from/to where it will get/put the input/output. Also. consider the data nodes as a whole (a cluster) , it all is the hdfs. Each node have a piece of your data (or not).